In 2007, the French TGV train set a world speed record by achieving a speed of 5

Question

In 2007, the French TGV train set a world speed record by achieving a speed of 575 km/h. At these speeds, most of the engine energy is used to overcome air resistance. The force due to air resistance in a test run was equivalent to the weight of 9.7 tonnes with g = 9.8 m/s2.  The mass of the TGV train was 241 tonnes. During a test run at 503 km/h, the crew decided that they need to stop the train. Assume that they could maintain the 9.7 tonne stopping force constant throughout the braking period. What distance did the train travel from the moment the crew started braking until the train stopped?

Explanation / Answer

M = 241 tonne = 2.41 * 10E5 kg

F = 9700 * 9.8 = 9.51 * 10E4

V = 503000 / 3600 = 140 m/s

2 a S = Vi^2       since the final speed is zero  

S = 140^2 / (2 * 9.51 * 10E4 / 2.41 * 10E5)      since a = F / M

S = 2.48 * 10E4 m = 24.8 km

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